Draftsman&#39;s rule.



UNITED STATES Patented January 31, 1905.

PATENT OFFICE.

ALBERT B. WILLITS, OF THE UNITED STATES NAVY.

DRAFTSMANS RULE.

SPECIFICATION forming part of Letters Patent No. 781,117, dated. January 31, 1905.

Application filed November 4, 1904:. Serial No. 231,414.

To all w/mm it may concern.-

Be it known that I, ALBERT BOWER WILLITs. of the, United States Navy, a citizen of the United States, residing in the city and county of Philadelphia and State of Pennsylvania, have invented a new and useful Improvement in Draftsmens Rules, of which the following is a specification. 7

My invention relates to tools used by draftsmen and others whose employment involves the use of similar tools; and it consists of a rule in which one of the edges thereof is combined with a plane, preferably placed at right angles to the flat side of the rule, and having suchv plane provided with a reflecting-surface for the purpose of utilizing the reflected image of lines previously drawn in the progress of the work in hand and by meansof which reflection a line can be readily and accurately drawn at right angles to the line so reflected, or the lines of any-plane angle may in like manner be readily and accurately bisected, or a circle may inlike manner be readily and accurately divided by diameters or its center quickly found and all this withoutthe use of Tvsquar.e, triangle, or otherdraftsman-tool as usually used for doing such work. I attain these results by such a rule as is illustrated in the accompanying drawings, in which-' Figure l is an end view of my improved rule. Figs. 2 and 3 are front views, and Fig. 4C is an isometrical view of the same,

Similar letters refer to similar parts in all the figures.

Referring to Fig. 1, the angle A a b is a right angle, the edge a is a straight edge, and the vertical face A, which comprises the surface D E e d of Fig. 2, is a plziinreflectingsurface.

To use the rule for drawing a line at right angles to one previously drawn-as line F G of Fig. 2, for instancethe exposed part of such line will appear reflected in such reflecting-surface, as'indicated by the dotted line G H or as V W from the line W Y in the same figure, which reflection when brought in line with the exposed line G F, as in the ease of the reflectionH G, will locate the edge of the rule at right angles to such reflected.

and its reflected image V W. Similarly if the rule is placed so that the reflected image of the exposed part of a circle makes a fair and true circle with that exposed part, as shown in Fig. 3, theedge D E lies on a diameter of the circle and passes through its center, so that a line traced along the edge of the ruler will be a diameter, and .thus by striking two different diameters, as is shown by the lines L L and D E, the point L of their intersection will be found to be the center of the circle K J, in which Q is the reflection of same. 'Theleast deviation of the edge D E from a true diameter of the circle K J will be indicated by a want of symmetry in the reflected image with the exposed line so reflected for instance, as is shown by the lineT U, indicating the reflection of the line M U. Similarly, also, if the rule is placedso that the image of the exposed part of any two intersecting straight linesas, for instance, as shown by S R in'Fig. i--are in line with the exposed part of the other of these lines, N P, the edge D E will direct a line which accurately bisects that angle made by the intersection of the lines in which the edge D E lies. It is obvious that the usefulness of my said rule is increased by having its edgesB and C graduated with a scale for measuring purposes, as is shown on the one edge of the rule illustrated by Fig- 4.,

Having thus shown and described my said invention and illustrated instances of its ap plication to practical uses, what I claim is 1. A rule composed of two flanges placedin planes at right angles to each other, with the exterior-side or face of one or of both of said flanges provided with a surface that will re- 2. A rule composed of two flanges placed in substantially as and for the purposes shown TO planes at right angles to each other, with the and described. exterior side or face of one or of both of said In testimony whereot'lhave signed mynamc flanges provided with a surface that will reto this specification in the presence of two sub- 5 fleet the image of lines drawn on a surface scribing witnesses.

lying in a plane with the exterior side or face ALBERT B. VVILLITS. of the other of said flanges, and having the Witnesses: interior side or face of one or both of said JAs. NELSON ALEXANDER, flanges provided with a measuring-scale; all R0131". D. KINNEY. 

